Despite the numerous strides that have been made in the last two decades in the development of diagnostic reagents and instruments, efforts continue to make diagnoses more accurate, simpler, and more available to non-technical personnel in a wide variety of environments. There is continuing interest in being able to carry out individual assays by non-technical personnel at such sites as doctor's offices, clinics, the home, rest homes, and the like. In order to ensure that non-technical individuals may accurately perform these assays, it is essential that the protocols be simple, there be few if any measurements, and the readings be relatively automatic.
For this purpose, it is desirable to have a disposable unit which can be used individually for each determination. The disposable can provide the various reagents which are necessary for the determination, serve to ensure their mixing, and allow for the proper fitting into a device which provides the final determination. In this manner, one can be relatively assured that assay determinations may be made rapidly and with a minimum opportunity for error in quantitation.
Even in clinical laboratories, there are many opportunities for measuring an analyte in an individual determination. Frequently, particular analytes may be determined only a few times in any one day, so that individual determinations will be the most efficient. Where one can use a disposable unit which only requires the addition of the sample to the disposable unit, great labor savings may be realized, since individuals of high technical qualification would not be required and accuracy would be relatively assured.
There is, therefore, a continuing need for devices employing disposable units, where the units allow for the performance of the assay protocol, with minimal measurement and input from the operator, while allowing for sensitive and accurate quantification of the amount of analyte in a sample.
A long-standing difficulty with disposable units has been efficient washing to remove unbound reagents from the measurement area. The present invention solves this problem by eliminating all side walls, which allows sequential orthogonal washing and leaves no stagnant areas where excess reagent could reside and interfere with the test measurement.